The Intrinsic Knowability of the Past

Among the general population, and especially in the United States, scientific theories concerning how things were in the past such as the theories of evolution and the big bang are politically controversial. I say politically controversial, because there is no scientific controversy whatsoever. Unfortunately, there are many political and religious leaders who go to great lengths to deceive the populace as to the real workings of science with disastrous consequences. Feeble rhetorical devices like asking “were you there?” get parroted by individuals whose deep ideologies line up with the deceivers. The “were you there” question is ultimately one of the most insidious arguments by science deniers, but also one of the most fallacious. It is built around the idea that without a direct account by human narrators, the past is fundamentally unknowable.

Unfortunately, as exemplified by fraudsters, perjurers, and people who mistake the planet Venus for an alien spacecraft, human beings are notoriously unreliable narrators. One only needs to look at the “satanic abuse” moral panic of the 80's and 90's to see that people don't have to be deliberately deceitful in order to provide accounts that are 100% baloney. Additionally, the concept of human narrators being the only way to know the past is undermined by the laws of physics themselves. In fact, the past being knowable is a fundamental attribute of the universe we live in.

In general, there are three principles that ensure that at least a partial record of past natural events and phenomena is recorded, and those are the Laws of Conservation of Mass and Energy, the natural laws governing radioactive decay, and the finite speed of light being a cosmic speed limit.

First of all, matter is energy, and energy can not be created or destroyed. Mass can not be fully converted to other forms of energy, except through nuclear processes. This means that in general, objects that existed in the past often leave a record that they were there. Geological events don't rewrite the records laid down by prior ones, so stratigraphy can be used to read the life story of the earth. A plant or animal may be dead for millions of years, and while its remains may undergo a chemical change and petrify, the remains still exist leaving a record of their past presence on the planet. The moon may not be in its original material form, but by studying its orbit and composition, we understand that all of the material that makes up the moon was once a part of the earth before a cataclysmic collision between worlds ejected the matter that would one day accrete to form our natural satellite. Likewise, a record of the age of all of these things is knowable due to to the constants of radioactive decay.

Fossilized remains of Tyrannosaurus - photo from Wikipedia

The finite and unchanging speed of light means that we have a perpetual visual record of the past. When we observe distant corners of the universe through telescopes, we look into the distant past as well. We can see galaxies and stars dating back to the earliest generations when light first began to propagate through space. When looking at the Andromeda galaxy through a backyard telescope, we are looking directly at the time when wooly mammoths and glyptodonts roamed the grasslands of the desert southwest during the ice age. By observing galactic spectra, we can measure the rate of universal expansion and even see how quickly that expansion is accelerating. From there we can see how long ago the universe itself began.

The Andromeda Galaxy (M31) - Photo from Wikipedia

These key thing to understand is that these principles were not imagined by mankind; they were discovered. They are fundamental truths that were waiting to be found. We are slave to them, as they govern everything in our experience. No amount of wishful thinking can change the fact that these principles provide an objective record of the nature of the past.

People may not be reliable narrators, but if there's one thing science has taught us it's that the universe itself is, and we must be willing to listen to the stories it has to tell us.